Ethan Dicks wrote:
Two reasons come to mind - one, to make this a passive
device off of
the parallel port that doesn't require an external power wart, and
two, because I'm at the South Pole and I have to work with what I have
on hand - there won't be another plane for nearly 4 months.
Can you make resistors out of ice? :-)
Lack of power on the parallel port's a strange one - I always found it hard to
believe that the implementors didn't forsee the use of the port as a
general-purpose output port and provide it with a couple of power pins. It's
not like there aren't several grounds available so that couple could have been
given up for +5V pins.
I used to power external gadgets from the PC keyboard port because I happened
to have the right connectors to hand in order to tap power from there - that
was at least portable until everywhere went to ps/2 type keyboards.
One of my other machines just had one of the internal drive power connectors
fed out of the back of the case though for a useful point to take power from.
cheers
J.